1. Field of the Invention
The present invention relates to a method of chamfering semiconductor wafers, and more particularly to the prevention of the occurrence of working distortions at the peripheral parts or portions of the wafers.
2. Description of the Prior Art
In the manufacture of a semiconductor device such as transistor and IC, a variety of treatments for forming elements are made wherein a single crystal semiconductor ingot is sliced and worked into semiconductor wafers by means of a diamond cutter or the like. Crystal distortions etc. are prone to arise at the surface and peripheral parts of the wafers due to the slicing operation.
Mechanical polishing or chemical polishing is therefore carried out for the surface of the semiconductor wafers obtained by the slicing. In the polishing, however, it is often the case that chips, crystal distortions and crystal defects are brought about particularly on the peripheral parts of the semiconductor wafers. The chips seem to be ascribable to the fact that although the semiconductor wafer is very hard, it is fragile, and the fact that stresses are concentrated on the peripheral part of the wafer during the polishing operation.
In polishing the semiconductor wafer, only the peripheral parts were previously treated with sandpaper etc. as a trial. Even by this trial procedure, the chips, distortions and crystal defects could not be eliminated.
Where a semiconductor layer was formed by epitaxial growth on such wafer, the temperature was more easily raised and a reaction gas pervaded more at the peripheral wafer than at the central part of the wafer. As a result, the growth rate became larger at the peripheral parts than at the central part, and a thicker layer called the crown was formed.
With the treatment by such mechanical means, the distortions due to the working appear at the peripheral wafer parts, and minute cracks appear. A further disadvantage is that the chipping of the peripheral parts of the wafer tends to arise during the working. Where the epitaxially grown layer is formed on the surface of the semiconductor wafer subjected to such working, the distortions and defects at the working affect the epitaxially grown layer, to disadvantageously cause slip lines and stacking faults.
These disadvantages seem to come from the fact that, with the treating method which employs the sand paper, working distortions are brought about or arise within the peripheral parts of the semiconductor wafer anew during this treatment.
In any event, it has been revealed that the mechanical method using the sandpaper or the like in the treatment of the semiconductor wafer is unsuitable.
Besides, the prior-art method of mechanical treatment works the wafers one by one, and is limited in the number of wafers which it can treat. When it is intended to treat many wafers, the equipment becomes large and the job efficiency becomes very inferior.